Health regeneration in trigger

Hello, I don’t know if someone asked this question before me, but can’t find it…
I want make script, where if player stands on some field, his current health will be regenerating. But there is a problem, that function OnTriggerEnter is not called per frame, so my current health is not regenerating smoothly, but it regenerates some of hp and then it will stop.
Here is the script I tried make:

var regenerationSpeed : float = 1.5f;

function OnTriggerEnter() {
    if(CharacterStats.TotalHP >= ManaAndHealth.curHP) {

    ManaAndHealth.curHP += Time.deltaTime * regenerationSpeed;

Maybe you wish to use OnTriggerStay.